Oscillating circuit for train-control systems



1929? T. E. QLARK El AL 1,737,750

OSCILLATING CIRCUIT FOR TRAIN CONTROL SYSTEMS Filed 001:. 23, 1925INVENTORS Patented Dec. 3, 1929 UNITED STATES PTENT; OFFICE THOMAS E.CLARK AND JAMES E. CLARK, or nnTRorT, MIonIGAn, ASSIGNORS To con-Trnuons TRAIN CONTROL CORPORATION, OF nRTnorT, MICHIGAN, A CORPORATION01? MICHIGAN OSOILLATING CIRCUIT FOR TRAIN-CONTROL SYSTEMS Applicationfiled October 23, 1925. Serial No. 64,353.

While testing the train control installation shown in our co-pendingapplication Serial Number 31,633, filed May 20, 1925, we found that theconductivity of the ballast between 5 the rails and the resistance andthe impedance of the rails were serious factors and that theelectromagnetic wave energy propagated in the track rails waseflectivefor limited distances only, depending somewhat on the wave lengths; Weexperimented with currents having wave lengths of from One thousand tothirty thousand meters and tried out vacuum tubes of from 5 to 250 wattscapacity. These tubes were used as transmitting oscillators, in somecases with transformers of alternating signal currents, and in othertests, using storage batteries and rotary dynamotors.

VVe' found that the electrical conditions in the rails were stabilizedby connecting a loading condenser across between the rails at a distancefrom the point where the current transmitting mechanism was connected tothe rails, these rails being divided into blocks and the transmitting orpropagating devices for the high-frequency currents being connected tothe exit ends of the blocks. With this loading condenser connectedacross between the rails, we found that the variations of dissipation ofcurrent due to wet, dry or frozen ballast between the condenser and thepoint of connection 'of the propagating device were not so marked.

We also found that when a loop collector coil mounted on a locomotive orother moving vehicle, is placed in this field of force and adjacent tobut spaced apart from one of the rails, and this coil is tuned toresonance with the electr-o-magnetic wave'energy in the rails, that aproper instrument such as a mille-am- )eremeter' connected in thiscollector circuit indicated an appreciable and effective currenttherein.

We also found that as the locomotive travelstoward the exit end of theblock, the collector coil circuits get out of tune with the trackcurrent circuits, due to the change of wave length of the current propaated in the rails, because of the change in the inductance of the trackcircuit, which resulted from the change in length of the oscillatingcircuit including the track rails. We discovered that this change inwave length could be rendered negligible by constructing the loadingcoil; of the current transmitting mechanism with a large number ofinductance turns so as to stabilize the wave lengths in the circuit ofthe track rails, including the locomotive axle moving thereon, and wefound that the collector coil and its circuit, when adjusted through aproper variable condenser therein, could then be easily made to respondto the electro-magnetic lines of force or flux created by the locomotiveaxle completing the oscillating track circuit.

Our invention, therefore, consists of means for propagatingelectro-rnagnetic wave energy in the rails of a railway track, thepropagating device being so constructed that the wave lengths of thesecurrents will not be unduly varied by a locomotive as it moves along therails of the energized section of tree It further consists in thedetails ofconstruction illustrated in the accompanying drawing andparticularly pointed out in the claims. 7

'In said prior application we have explained the transformer forpropagating high-frequency electro-magnetic waves in the track and howcollector coils mounted on the locomotives and tuned to these wavespicked up currents which so affected certain instrumentalities on thelocomotives as to control their operation. This transformer comprises avacuum tube 38 having a plate 45, a grid 42 and a filament 37. Thisfilament is heated by the battery 13 whenever its circuit is closed,which occurs when the track section between the insulations 3 in therails 1 and 2 and the condenser 20, is occupied by a train T,shortcircuiting the relay 7 normally energized by battery 8, whichpermits its armature a to close the circuit from the battery over wire12, lilament37, wire 14, adjustable resistance 39, wire 10, armature 7and wire 11. The main oscillating circuit consists of the wires 15 and10, the resistance 39, wire 14:,filament 37, across the tube to theplate 45', wire 4:8, coil 4:7 and wire 46 to the battery 36'. Thefrequencies and wave lengths are controlled by the adjustable con-denser50 which shunts the plate coil 47. This battery 36 is usually termed theB battery and is preferably of 350 volts. Any other proper source ofcurrent may be employed.

The loading coil 52 connects to the wires 5 and 6, which connect therelay 7 to the rails, by means of wires 32 and 33, a condenser beingprovided to prevent the passage of direct signal currents and the shortcircuiting of the track circuit. This coil 52 and its con necting wires,the rails 1 and 2 of the section between the wires 5 and 6 and thecondenser 20, and this condenser 20, constitute the output oscillatingcircuit. The electro-magnetic waves of this circuit may be used toaffect instrumentalities on the locomotive passing over this tracksection which are tuned thereto, at which time the leading or pilot axleof the locomotive and the wheels there-on affect these wave lengths tosome extent.

The inductance of the coil 52 and its wires, of the condensers-35 and 20and of the axle and wheels remains constant, but that of the rails ofthe section, which may be two hun dred or more feet in length, isreduced as the locomotive moves from the condenser 2O to-- ward theinsulations 3. This change was found suiiicient to so vary theelectro-magnetic wave lengths in this oscillating circuit thatinstrumentalities on the locomotive which were tuned to the wave lengthswhich were present when the locomotive was at the condenser 20 were notaffected when the locomotive reached the exit end of the section. I IThe loading coil can easily be wound to have from 40 to 50 milihenrys ofinductance and when a condenser 20 of fairly large ca p'acit-y isemployed, the change in wave lengths of the currents in this oscillatingcircuit need not be more than 50 meters, or not morethan one per cent.If the collector circuits onthelocomotive are tuned to the wave lengthswhich are present when the leading axle of the locomotive is at themiddle point of the controlled track section, these collector coils willrespond to the electro-magnetic waves throughout the length of suchsection, especially as such instrumentalities respond to currents whosewave lengths vary two or even more per cent.

The details of construction of the mechanism described and theproportions of the parts may all be changed by those skilled in the art"without departing from the spirit of our invention, as set forth in thefollowing claims.

We claim 1. Means for controlling the operation of railway trainscomprising a track divided into control sections, a condenser connectingthe rails at one end of each section, and means connected to the railsat the opposite end of such section adapted to propagate high-frequencyelectro-magnetie waves therein, said means embodying a loading coilconnected directly to the rails and having a greater inductance than therails of said section.

2. Means for controlling the operation of railway trains comprising atrackdivided into control sections, and means connected to the rails atone end of each section adapted to propagate high-frequencyelectro-magnetic waves therein of proper lengths to atfeetinstrumentalities 'on' locomotives passing over such sections, saidmeans embodying a coil of such high inductance that the lengths of thewaves in the rails of such section will not be varied sufficiently bythe shortening of the track circuit when the locomotive passes over suchsections as to pass out of the range of the instrumentalities on suchlocomotive.

8. Means for controlling the operation of railway trains comprising atrack divided into control sections, and a transformerconnected to therails at one end of each control section adapted to propagatehigh-frequency electromagnetic waves therein of proper wave lengths toaffect instrumentalities on locomotives passing over such sections, saidmeans embodying an inductance coil of three Widings comprising a gridcoil, a plate coil and a loading coil, all in resonance with each other,the loading coil being of such high inductance that the lengths of thewaves in the rails of such section will not be varied suiliciently bythe shortening of the track circuit when the locomotive passes over suchsections as to pass out of the range of the instrumentalities on suchlocomotive.

4. Means for controlling the operation of railway trains comprising atrack divided into control sections, and means connected to the rails atthe opposite end of such section adapted to propagate high-frequencyelectromagnetic waves therein, said means embodying a loading coilconnected directly to the rails and having a greater inductance than therails of said section.

5. Means for controlling the operation of railway trains comprising atrack divided into control sections, and means connected to the rails atone end ofea'ch section adapted to propagate high-frequencyelectro-magnetic waves therein of proper lengths to affeetinstrumentalities on locomotives passing over such sections, said meansembodying means of such high inductance that the lengths of the waves inthe rails of such section will not be varied sufliciently by theshortening of the track circuit when the locomotive passes over suchsections as to pass out of the range of the instrumentalities on suchlocomotive.

THOMAS E. CLARK.

JAMES E. CLARK.

